In a manufacture process of a semiconductor substrate having a multilayer film structure and a device process using the substrate, it is important to detect various defects on a surface and in the close vicinity of the surface, which affect a device yield, upon process management and improvement of the yield. In recent years, SOI wafers are used for device fabrication as the semiconductor substrate having a multilayer film structure, and processes are thereby complex. As devices have become finer, the importance of optical inspection has been increased from the viewpoint of inspection capability or throughput.
Examples of the above-described defects to be an inspection object on the surface and in the close vicinity of the surface include crystal defects, extraneous substances, scratches, pattern defects, and deposited abnormal patterns. A dark-field inspection method using scattered light or a bright-field inspection method using a microscope is used to detect the defects.
For example, there are disclosed an inspection method of a semiconductor substrate by detecting the scattered light when laser light is irradiated to the semiconductor substrate (See Patent Literature 1), and a surface inspection method for an inspection subject, where two or more kinds of laser are switched or mixed to make the laser incident on the inspection subject by a same incident angle (See Patent Literature 2).